Polymerization of isoprene with catalyst of transition metal and polyiminoalane

ABSTRACT

1,131,257. Polymerization catalysts for butadiene. SNAM S.p.A. 4 Nov., 1965 [3 Feb., 1965], No. 46885/65. Heading C3P. A polymerization catalyst comprises (a) a transition metal compound of a metal of Group IV to VIII of the Periodic System, (b) a linear aluminium polymeric compound containing repeating units of the formula where R is an aryl, alkyl, or cycloalkyl hydrocarbon radical, and (c) if component (a) is free from cobalt, iodine is present therein or is introduced in the form of aluminium iodide whilst if cobalt is present any aluminium halide can be present. Compound (b) may be made by reacting LiAlH 4  with the hydrochloride of a primary amine or by reacting a primary amine with an aluminium hydride. Compound (a) may be TiCl 3 , TiCl 4 , TiI 4 , VCl 3 , VCl 4 , TiI 2 Cl 2 , NiCl 2 , VOCl 3 , CoCl 2 , or cobalt acetylacetonate. The (c) compound may be AlI 3 , AlCl 3 , or AlBr 3 . In the examples the R in the (b) polymer is ethyl, n-butyl, and phenyl. The catalyst is used to polymerize butadiene in the presence of a hydrocarbon solvent. The polymer is recovered by conventional techniques.

United States Patent US. Cl. 260-943 1 Claim ABSTRACT OF THE DISCLOSURE stereospecific polymers, and more particularly 1,4 cis polyisoprene, are obtained from conjugated dienes containing at least four carbon atoms in their molecule by using a catalytic system containing, in addition to a compound of a transition metal of the IV to VIII group of the periodic system, an aluminum polymeric compound of polyiminic nature having in its molecule repeating units of the type:

-A1N-] t l where R is an alkyl, aryl or cycloalkyl hydrocarbon radical. The polymerization is effected in an aliphatic hydrocarbon solvent at a temperature between -30 C. and 100 C. and at a pressure between one and fifty atmospheres.

The present invention relates to a new catalytic system for stereospecific polymerization of conjugated dienes and to the polymerization process using said catalytic system.

The preparation of polydienes having high regularity of structure is well known using catalytic systems comprising transition metal compounds and alkyl aluminum compounds.

In particular it is possible to prepare for example, 1,4- cis polyisoprene with catalytic systems comprising TiCl, and trialkyl aluminum.

With the same catalytic systems and changing the compositions of the catalytic system components it is also possible to obtain 1,4-trans polyisoprene.

Since said catalytic systems contain alkyl aluminum compounds, they have a disadvantageous instability typical of these organometallic compounds, which are easily attacked by moisture, oxygen etc.

On the other hand, it must be considered that polyisoprene obtained in such a way rarely has high values of [1;], i.e. high molecular weights, which, if nothing else, makes it necessary to separate the low molecular weight polymers, which cannot be utilized for example in the tire industry.

We have now found that it is possible to obtain stereospecific polymers from conjugated dienes containing at least 4 carbon atoms in their molecule by using a catalytic system containing, in addition to the transition metal compound, an aluminum polymeric compound of polyiminic nature containing in its molecule repeating units of the type:

where R is an alkyl, aryl or cycloalkyl radical. Said compounds can be easily prepared by reacting LiAlH, with 3,476,734 Patented Nov. 4, 1969 "ice amine hydrochlorides or by reacting A1H with primary amines:

nRNHz-HC1 nLiAlH;

where R and R, being the same or ditferent, are chosen from hydrocarbon aryl, alkyl or cycloalkyl radicals such as, for example: CH C H nC I-I C H In the course of the description said compounds will be also termed aluminum iminic polymers. Said preparations are described by E. Wiberg, A. May in Z. t. Naturforsch, 10b, 232 (1955) and in particular by R. Ehrlich and coll. in Inorg. Chem. 3, 628 (1964). Molecular weight measurements show them to be polymers having n 4. When n is small (from 4 to about 50), said compounds are soluble in aromatic and at times aliphatic solvents. Higher molecular weight polymers are insoluble in common solvents although they are still etficient as catalysts in the presence, for example, of TiCl since they still contain an equivalent of active hydrogen for each aluminum atom.

Said compounds, principally in contrast to the alkyl aluminum compounds used in the traditional art, olTer the advantage of a higher stability towards oxidizing and hydrolysing agents and better handling.

The use of said catalytic systems makes it possible, in particular, to obtain, from isoprene, polyisoprene having a high ratio of 1,4-cis units (higher than 92%).

Furthermore it has been found that operating under suitable conditions it is possible to obtain 1,4-cis polyisoprene having an intrinsic viscosity higher than S, which corresponds to a viscosimetric molecular weight of about 1,500,000; said high molecular weight polyisoprene has the advantage of better mechanical properties in the vulcanized articles. The transition metal compound, which makes up the catalytic system together with the aluminum iminic polymer, can be selected from titanium tetrachloride, tetrabromide and tetraiodide, vanadium trichloride, zirconium tetrachloride, cobalt chloride, cobalt acetylacetonate; manganese chloride, nickel chloride and the like.

When the desired polydiene is 1,4-cis polyisoprene, the ratio between the aluminum gram atoms in the polyiminealuminum to gram atoms of transition metal must necessarily be in the range between 1.1 and 2.

The reaction can be carried out in inert hydrocarbon solvents, such as aromatic, aliphatic, cycloaliphatic hydrocarbons and mixtures thereof; in particular, if isoprene polymers having 1,4cis structure and high molecular weight are to be obtained, the reaction is carired out in alipahtic hydrocarbon solvents, e.g. n-hexane, n-heptane, n-octane and the like.

Using said aliphatic solvents polymers are obtained having a high intrinsic viscosity, between 5 and 8, corresponding to a molecular weight of 1,500,000.

The catalytic system of the present invention can be formed in advance by interaction of the aluminum iminic polymer with the transition metal compound or it can be formed by interacting the two components of the catalytic system in the presence of the monomer to be polymerized.

Among the monomers which can be advantageously The same procedure was followed for all the described used are the conjugated dienes having in their molecules polymerization runs. up to 12 carbon atoms, among them butadiene, isoprene, The results obtained in isoprene polymerization using 1,3-pentadiene, 1,3-hexadiene, dimethyl-butadiene, phenthe aluminum ethyl-iminic polymer and diflerent Al/Ti yl-butadiene and the like can be mentioned. ratios are shown inTable 1.

TABLE 1 Al-N Solid Polymerpolymer IR Analysis 02115 n Molar izatiou yield, Total un- (Solution A) ratio, time percent 1,4-cis, 1,4-trans, 3,4, 1,2, saturation,

cc. Al/Ti (hrs.) g. percent percent percent percent percent [1;]

TiCl; 1.82 mmoles, Toluene 100 cmfi, Isoprene 30 cm Polymerization temperature C. The reaction can be carried out at temperatures be- EXAMPLES 5-9 11 n r u i w n tween 9 C a d +100 a d at p 688 res bet e6 Into a 500 cm. two neck flask provided with reflux atmospheric and 10 atmospheres.

cooler and magnetic stirrer, 8.2 g. (0.216 mole) of The l fi l l .meant to Illustrate the LiAlH and 200 cm. of anhydrous toluene are intropresentmventlon wlt out lmltmglt' duced. To this suspension 17.7 g. (0.195 mole) of n- EXAMPLES l-4 butylamine hydrochloride are added for about 45 min- 5 g. of LiAlH (0.132 m 01 e) and 130 of anhy utes. The mixture is stirred at 50-55 C. for 3 hours, then drous benzene are introduced into a two neck flask prol room temperature for another 0 hours The mlxture vided with a reflux cooler is then filtered and the clear solutlon concentrated under To the stirred suspension, 9.45 g. (0.116 mole) of valcuum 3:9 tenipergture to about of Its Initial eth lamine h drochloride are added during about V0 an 1513 am yse miri utes at roo in temperature. The mixture is continuously 30 A1=258 'q g'/1OO cm'a; H(ac stirred at C. for 16 hours and at room temperature tlve):2558 l /100cm' ;Cl?n0ne' for another 35 hours. The mixture is filtered under nitro- The 'imfllysls corresponds with good approxlmatlon to gen to obtain a solution which when analysed gives the the empmcal formula:

following results:

Al= 2.25 g./100 cm. N=l33 g./10O cm. Cl=0.l0 35 H 1 1: ,o, g./100 cm. H(active)=1620 cm. /l00 cm. which cor- I: 6

respond with a good approximation to an empirical formula:

H F N I AFN C H 40 This solution is called solution B.

T I J t 2 Following the above mentioned procedure, polymeriza- H 2H5 n t1on runs in toluene and n-heptane were carried out, the Such solution is called solution A, results of which are shown in Table 2.

TABLE 2 b H n04 Ho Solid Polymerpolymer IR Analysis l-N Molar Polymerizatlon yield, Total (Solution B) ratio, lzation time, percent 1,4-cis, 1,4-trans, 3,4, 1,2, unsat.

cm. Al/Ti solvent hrs. g. percent percent percent percent percent [r 2. 2 1. 1 Toluene 2 61. 5 95. 5 0 4 0. 5 96 3. 5 2.31 1.2 do 2 36.3 95.5 0 4 0.5 96 2.63 2. 31 1. 2 n-Heptan 16 73 96. 5 0 3. 5 0 94 5. 29 2. 5 1.3 do 16 85 96. 5 0 3. 5 0 95 6. 08 2.7 1.4 d0 16 68.2 96 O 4 0 93 5.15

b TiCh 1.82 mmoles, solvent 100 cmfi, isoprene 30 cmfi, polymerization temperature +15 C.

We have carried out polymerization runs of isoprene with a catalyst obtained by mixing, in convenient ratios, EXAMPLES 10-11 solution A with a toluenic solution of TiCl The polym- 3 erization runs have been carried out in 200 cm. capacity Into a 500 two neck flask provlded Wlth reflux drinking bottles introducing successively: 100 cm. of ancooler and magnetic stiffer, gof LiA1H4 hydrous toluene, 1 cm. of a 1.82 molar toluenic solumolel and 0 of toluene are Charged- To this $118- tion of TiCl and the desired quantity of solution A. pension 13.1 g. (0.168 mole) of aniline hydrochloride Mixing was carried out While Stirring and in an inert are added during 30 minutes. The mixture is stirred at gas atmosphere- The bottle was then Closed with a f 5 room temperature for 75 hours and finally heated to prene plug and a bored crown metal cap, through WlllCh 50450 for 8 hours The mixture was filtered; and

3 30 of lspprene were Introduced by means of a by 20% of its initial volume is carried off by concentrating podermlc syr1nge.

The bottle was kept in a thermostatic bath at +15 under Vacuum C. for the desired time. Analysis is carried out on the obtained clear solution.

At the end, methanol was added together with an Th r s lt r A1=0 719 /100 cm, and also antioxidizer and the polymer coagulated and washed at length. Finally it was dried at 45 C. under vacuum until constant weight was reached. On the dry polymer, the yield was calculated and the IR analysis performed; and the intrinsic viscosity in toluene at 30 C. measured.

g. atoms H g. atoms N g. atoms Al g. atoms Al 6 Cl=none, which correspond with good approximation wherein to an empirical formula: R is an alkyl, aryl, or cycloalkyl radical, and

n is 24 in a hydrocarbon solvent, wherein the ratio between said polyiminoalane and the said compound of a transition metal is between 1.1 and 2,

and carrying out the polymerization reaction at temperatures between -30 and +l00 C. and at pres- This solution is called solution C. Results of isoprene polymerization runs with the aluminum phenyliminic polymer and TiCl carried out folsufes betWeFn 1 and 50 so that a P y is lowing the above outlined procedures, are shown in tamed having a 1,2 units content which is lower Table 3. than 1%.

TABLE 3 H C(iHs Solid 1 I polymer IR Analysis AlN n Molar yield, Total un- (Solution 0) ratio, percent 1,4-cis, 1,4-trans, 3,4, 1,2, saturation,

cmfi Al/Ti g. percent percent percent percent percent [1 Run No 'liCh 1.82 mmoles, Toluene 100 cm. Isoprene 30 cm}, polymerization temperature +15 0., polymerization time 2 hrs. What we claim is: References Cited 1. A process for polymerizing isoprene to substantially UNITED STATES PATENTS 53 f g li gggg g ff fggfiiw r 2,694,053 11/1954 Uraresh et al 260-946 a c y f t t d f th 29 3,165,503 1/1965 Kahn et al. 260-943 a compoun a ran110f1 me a 86 9 6 3,255,169 6/1966 Kearly 260-946 group conslsting of tltamum tetrachlonde, t1tan1um 3,163,611 12/1964 Anderson et aL tetrabromide, titanium tetraiodide, vanadium trichlo- 3,245,976 4/1966 Marconi et aL 260 943 ride, zirconium tetrachloride, cobalt chloride, cobalt acetylacetonate, manganese chloride and nickel chlo- 30 OTHER REFERENCES ride and The Chemistry of Alane, Polyiminoalanes by Ehrlich a polyiminoalane represented by the formula: at Inorganic Chemistry y 1964- JOSEPH L. SCHOFER, Primary Examiner 35 W. F. HAMROCK, Assistant Examiner i US. Cl. X.R. 

